SEVENTH ANNUAL MEETING 103 



the coal beds, and they appear to be of the same general nature 

 as the bedding planes mentioned above. They are often rather 

 uniform in thickness over considerable areas, but in places they 

 thicken for some distance and in others they thin down to 

 knife-edge partings. When the coal is split along well de- 

 veloped dull laminae the cleavage planes almost always show 

 distinct mineral charcoal surfaces. The bright laminae ap- 

 pear to be quite homogeneous in structure. 



The features above described are not peculiar to Illinois 

 coals. H S. Rogers and others have noted the alternations of 

 laminae of bright and dull coal, and the predominance of min- 

 eral charcoal in the dull laminae in the coals of the Appalachian 

 region, and the writer has observed the same characters in the 

 coals of Iowa. They have been described from coal beds gener- 

 ally in different parts of the world. The mineral charcoal is so 

 constantly present, and so intimately mingled in, and consti- 

 tutes such an important part of the dull laminae of the coal 

 that they must have been developed together ; in fact, the dull 

 appearance of these laminae in relatively pure coal beds is due 

 for the most part to the presence of mineral charcoal in these 

 bands. 



THE ORIGIN OF "MOTHER COAL" OR MINERAL CHARCOAL 



Two main explanations have been proposed to account for 

 the origin of mineral charcoal. One of these, held by many 

 paleobotanists and chemists in recent time, explains the min- 

 eral charcoal as formed from real charcoal derived from plant 

 tissues which resulted from forest fires sweeping over land 

 areas, the charred fragments being subsequently swept by 

 flooded streams into the basins where they were deposited with 

 the mass of vegetable matter there in process of accumulation. 



This explanation assumes that a considerable part of the 

 vegetable matter of the coal was transported material, which 

 assumption is open to all of the objections to the "transport" 

 theory mentioned above. It assumes that a very important 

 proportion of the coal was derived from plant tissues that 

 had been charred by fires previous to their accumulation, and 

 that these charred fragments had been carried into the coal 

 basin by streams in such enormous quantities as to cover the 

 surface of practically the entire area of the present coal beds, 

 5000 to 8000 square miles or more in extent ; that this process 

 took place not only once but was repeated as many times as 

 there are persistent dull charcoal-bearing laminae ; requiring 

 scores or hundreds of recurrences of such charcoal deposition 



